Tubular cracking furnace



Sept. 16, 1969 s. T. JURIC TUBULAR CRACKING FURNACE 4 Sheets-Sheet 1 Filed July 5, 1967 E BURNERS Fie INVENTOR. SLAVKOJURIC B P HIS ATTORNEY Sept. 16, 1969 s, JURI TUBULAR CRACKING FURNACE 4 Sheets-Sheet 2 Filed July 5, 1967 INVENTOR.

SLAVKOIJURIC BY P 021%& M

HIS ATTORNEY 4 Sheets-Sheet 4 INVENTOR.

SLAVKO JURlC HIS ATTORNEY Sept. 16, 1969 s. T. JURIC TUBULAR CRACKING FURNACE Filed July 3, 1967 United States Patent O 3,467,503 TUBULAR CRACKING FURNACE Slavko T. Juric, 8 Eschborestr., 6231 Schwalbach, Germany Filed July 3, 1967, Ser. No. 650,904 Claims priority, applitirnssGsermany, July 4, 1966,

U.S. Cl. 23-288 6 Claims ABSTRACT OF THE DISCLOSURE A tubular reaction furnace for cracking hydrocarbons at high temperatures and pressures for the extraction of synthess gases in which the reaction pipes are rigid at their lower ends with collecting tubes and have their upper ends projectng through the furnace bottom. The reaction pipes in the lower part and collecting tubes are fitted with internal insulation. The insulation in the lower part of the reaction tubes can be removed in order to replace the catalyst contained theren.

BACKGROUND OF THE INVENTION There is a multitude of known types of tubular cracking furnaces in which the pipes are arranged in the firing space in the form of registers or bundles. In this case the pipes can themselves contain tower packng or catalysts, for the control of the chemical reaction. When using simple tubes, the tubes are arranged vertically in the firing space in order to facilitate the changing of the pipe filling. The pipes can be either supported at their upper ends or lower ends. However it is also possible to hang the pipes either by their upper ends, or only to support them with their lower ends and letting them protrude with their free end into the firing space. Both arrangenents make it possible, for nstance, to avoid thermal stresses caused by temperature changes. The reactant is introduced into the crackng pipes by way of a distribution system and extracted at their ends by a collector system. There exists a known form of execution which in principle corresponds to the one shown in FIGURE 1.

The distribution system 1 is connected to the cracking pipes 3 by means of narrow pipes 2. By way of tube coils 4, the reactant reaches the collector Conduit 5, which is located in one or more firebrick lined chambers 6 and is protected against heat loss by insulation. As the Operating temperature can reach up to 1000 C. and the reaction takes place at a pressure of 20-40 atmospheres, the cracking pipes are very highly stressed. However this is also the case with the collector system. For this reason it was necessary heretofore to construct the entire length of the crackng pipes as well as the tube coils between the cracking pipes and the collector line itself of high alloy steel.

At the same time, the thermal expansion of the collector line and the connecting pipes has to be considered care'fully. Difficulties are especially encountered with the collector lines during manufacture and assembly and also during repairs. Furthermore, the steel employed is highly sensitive to rapid temperature changes on account of its austenitic structure.

SUMMARY OF THE INVENTION It has been found that the disadvantages inherent in the known forms of Construction can be avoided, if the reaction pipes which protrude vertically into the firing space are directly and solidly connected to the collectors which are located below the furnace, so that a rigid system is formed by the pipes and collectors, and the collector lines and the lower ends of the cracking pipes are insulated on 3,467,503 Patented Sept. 16, 1969 their inside up to approximately the upper edge of the furnace bottom.

The arrangement according to this invention exhibits a multtude of advantages when compared to the known system. Through the omission of the pigtails, the path of the gas from the crackng pipes to the collectors is kept as short as possible. Thereby the pressure drop and thus the energy expenditure in the lower part of the system is reduced. As the next part of the system located under the furnace bottom is insulated on the inside, it is possible to employ carbon steel and to reduce thermal expansion to a great extent.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE l is a vertical sectional diagrammatic elevation of a tubular reaction furnace according to the prior art;

FIGURE 2 is a fragmentary sche-matc perspective view of a furnace according to the invention in which the reaction pipes project through the bottom of the furnace and the lower ends are rigid with the collecting pipes;

FIGURE 3 is an enlarged vertical sectional elevation of one of the reaction pipes shown in FIGURE 2 and its connection to its collecting pipe; and

FIGURE 4 is an enlarged vertical sectional elevation of an alternate form of reaction pipe and collecting pipe assembly.

DESCRIPTION OF PREFERRED EMBODIMENTS Herein, FIGURE 2 shows the principle of the arrangement of the invention. 'Ihe collector lines 1, which contain the brick lining 2 are fitted with connecting headers 3. Onto these are flanged the reaction pipes 4 which enter through the furnace bottom 5.

FIGURE 3 shows details of the lower part of the reaction pipes and of the connections with the collector system. The collector line 11 contains an nner insulation 12. To this collector line are attached headers 13 with flanges 14. An insulating piece 15 is arranged on the inside of the header and fits into the insulation 12 of the collecting line. The flange 14 is connected to the inside insulation 12 and to the connecting flange 18 of the reaction pipe 19 by a spacer 16. This reaction pipe contains insulating form pieces 20, which extend to approximately the upper edge of the furnace bottom 21. Seated on the upper insulation form piece is a catalyst carrier 22. This carrier is perforated and prevents entry of the catalyst into the inside of the gas conduit. Emptying of the catalyst is carried out by removing the spacer pieces 16 and loosening of a holding device 23 'for the insulating form pieces 20. These form pieces are then withdrawn downwardly so that the free outow of the catalyst is made possible.

Another form of the invention is shown on FIGURE 4. The insulated collector line 11 is rigidly connected with lower pipe ends 24 by means of a smilarly insulated header 13. In a widened section 25 of the insulation of the connecting header, tubes 26 are inserted and these project into the lower section of the reaction pipe 24. The upper end of each tube 26 is provided with a number of holes through which the reactant gas can enter into the inside of the pipe. The annular intermediate space between the pipe 24 and the tube 26 is filled with an insulating material 27 to approximately the upper edge of the furnace bottom before the catalyst filling is introduced into the reaction pipe. An evacuating header 28 at the lower end of the pipe 24 is closed by a cover 29. In order to remove the catalyst, the cover 29 is removed and then the insulation removed. Therea'fter, the catalyst can pass freely from the reaction pipe. Such form of Construction has the advantage that leakage can only occur at the covers 29 and not at the 'load carrying connecting places, thereby increasing the safety of the operation.

Of course it is possible to shape the cracking pipes as double pipes, such as hairpin pipes, or, to combine a plurality of pipes into pipe registers. Finally, it is possible to arrange the distribution and collecting lines of such pipe registers in an inclined manner so that a continuous replacement of the Catalyst at every new charge of the furnace becomes possible.

What I claim is:

1. Tubular furnace for the indirect heating of crackable media, especially for the cracking of hydrocarbons 'for the extraction of synthesis gases, fuel gas and hydrogen, said fumace having a bottom wall below the firing space, vertically disposed reaction pipes extending through the bottom wall of the furnace into the firing space, a collector pipe disposed beneath the furnace and to which the lower ends of said reaction pipes are rgidly connected and supported, thermal insulation within said collector pipes, and thermal insulation within said reaction pipes extending approximately to the bottom wall of the furnace in the portion of pipe outside the firing space.

2. Tubular furnace as claimed in claim 1, comprising removable spacers connecting said reacton pipes, which have Catalyst contained therein, respectively to said col lector pipe to enable removal of the insulation from said reaction pipes after removal o'f the spacers thereby to replace the catalyst contained therein.

3. Tubular furnace as claimed in claim 1, comprising a tube disposed coaxially within and spaced from the walls 4 of a reaction pipe, said tube being arranged in the lower portion of the reaction pipe.

4. Tubular furnace as claimed in claim 3, comprising thermal insulation in the space between said tube and the Walls of said reaction pipe.

5. Tubular furnace as claimed in claim 4, comprising emptying headers in the reaction pipe at the lower level of insulation for enabling removal of the insulation and catalyst.

6. Tubular furnace as claimed in claim 1, in which said reaction pipes are arranged in pairs of generally hairpin shape.

References Cited UNITED STATES PATENTS 1,811,621 -6/1931 Fairchld 196-133 XR 1,851,999 5/1932 Black 196-133 XR 2,894,826 7/1959 Stengel 23-288 3,029,798 4/ 1962 Folds 122-494 3,189,371 6/1965 SWan 138-149 WILBUR L. BASCOMB, JR., Primary Examiner D. EDWARDS, Assistant Examiner us. c. X.R. 

